First Battle of Breitenfeld

The First Battle of Breitenfeld occurred on 7 September 1631 during the Thirty Years' War. The army of the Swedish king Gustavus Adolphus decisively defeated and annihilated a large Catholic German army near Leipzig, Saxony in the Protestants' first major victory of the war.

Background
Gustavus Adolphus' 23,000-strong Swedish army ravaged the Catholic German strongholds of Kustrin and Frankfurt an der Oder in an attempt to convince the nearby Protestant principalities to join him in his campaign of Swedish Intervention against the Holy Roman Empire in 1630. He did receive aid from Brandenburg and Saxony, but most German states saw him as an unwelcome invader. In September 1631, the Imperial general Count Tilly and his 35,000-strong Catholic League army marched into Saxony and met Gustavus Adolphus and John George I of Saxony's 28,750-strong army in battle at Breitenfeld.

Battle
The Protestant army consisted of 24,000 Swedish veteran troops and 18,000 Saxon troops, who were kept separate; the Swedes were organized into seven infantry brigades in two lines with 51 field artillery pieces and 4 3-lber guns attached to each infantry regiment. The Imperial army of 35,000 troops included 7,000 exhausted reinforcement troops, and their troops were organized into 12 large tercios with 2 further battalions on each flank to support the cavalry; they had 27 field artillery pieces.

At midday, the battle began with a 2-hour exchange of artillery fire between the two sides. The Swedes fired 3 to 5 volleys for each Imperial volley and targeted the deeper and densely-packed Imperial tercios, and 4,000 Imperial cuirassiers on Tilly's left wing, led by Gottfried zu Pappenheim, attacked Johan Baner's Swedish cavalry, but to little effect. Swedish musketeers fired on the cavalry at point-blank range and blunted the Imperial attack before the Swedes counterattacked, having repelled seven Imperial assaults. The depleted Imperial horse was forced to flee the field, but 4,000 Catholic League and Croatian horse charged the Saxons on the right flank, followed by the tercios advancing in an oblique order formation. The untrained Saxon infantry was overwhelmed, forcing the entire Saxon force to rout and exposing the Swedish flank. Marshal Gustav Horn quickly pulled back before the tercios could regroup and change direction, and he then launched a counterattack with his cavalry, while the high-firepower Swedish arquebusiers and cannon repelled an Imperial attack. Baner's cavalry, now directly led by Gustavus Adolphus, attacked the lightly-defended Imperial left, capturing the stationary Imperial cannon and turning their cannon on their owners. Lennart Torstenson then had his lighter and more flexible Swedish guns hit the Imperials from another side, and the Imperial forces collapsed; Tilly and Pappenheim were both wounded. 7,600 Imperial soldiers were killed and 6,000 captured, and the Catholic army was utterly annihilated and had to be rebuilt from scratch. Gustavus Adolphus' victory convinced several Protestant princes to join Gustavus' army.